1. Field of the Invention
The present invention relates to the field of locks and more particularly to an apparatus for and method of rekeying a pin tumbler lock having tumbler pins, driver pins and at least two master pins without disassembly of the lock apparatus or removal or replacement of any master pins therefrom or therein.
2. Description of the Prior Art
Pin tumbler locks are widely used in providing security for commercial facilities. Such locks are sold in different embodiments, including mortise, rim, key-in-knob, and padlock cylinders.
A standard pin tumbler lock can be rekeyed by removing the plug that contains the tumbler pins and that is rotated to operate a latch or bolt. Such rekeying, of course, first requires removal of the lock from the door, for example, in which it is mounted. Then the lock is disassembled by removal of the plug and inserting different height tumbler pins in the plug, re-assembling the lock and re-installing the lock in the door.
The prior art includes hundreds of examples of ways in which locks can be rekeyed without removal of the lock from the door and without disassembling the lock. Numerous examples use the pin tumbler principle, such as shown in U.S. Pat. Nos. 2,325,358 to Hull and 2,427,837 to Connell. However, these have not used the standard pin tumbler lock construction which is of minimum size and is manufactured in relatively limited, standard varieties. As another example, U.S. Pat. No. 2,113,007 to Swanson shows complex sleeves and sleeve actuators between the plug and the housing of a pin tumbler lock, which requires major redesign of an existing pin tumbler lock. Other examples that do not use such a sleeve require enlarged, non-standard housings that are provided with additional pinways, driver pins and springs to provide a supply of master pins that can be interposed in the pin stacks of the enlarged pin tumbler lock for rekeying.
Others have attempted to rekey standard pin tumbler locks by making relatively minor modifications thereto. Such modifications only allow a limited number of different key combinations before the lock must be removed from the door and disassembled. See, for example, Smith U.S. Pat. No. 4,440,009, in which the rekeying is done by removing master pins from the lock. Another embodiment disclosed in the U.S. Pat. No. 4,440,009 inserts master pins into the lock, which requires dexterity and knowledge of the internal construction of the lock.
Despite these numerous attempts to enable pin tumbler locks to be rekeyed without removal from the door or disassembly of the plug from the housing, or without removing master pins from or adding them to the assembled and installed locks, to applicant's knowledge there has thus far been no pin tumbler lock made in commercial quantities that is rekeyable in a simple manner while assembled and installed in a door, and that can be manufactured by making a minimum of modifications to a standard pin tumbler lock and that provides extensive quantities of different key combinations.
Applicant's own prior efforts have provided some of these features, but have required a certain amount of skill on the part of the person doing the rekeying. Thus, even though such prior efforts have simplified and reduced the time required for a locksmith to rekey a pin tumbler lock without disassembly or removal from the door, a still simpler rekeyable lock based on the standard pin tumbler principle is required in order to make rekeyable pin tumbler locks available for everyday use. For example, maintenance personnel who are not trained as locksmiths but who must frequently and quickly rekey locks, find it desirable to be able to select from a substantial quantity of different key combinations. Also, landlords could reduce operating costs if an easy to rekey, pin tumbler lock were available as a replacement for the standard pin tumbler lock.